Refrigeration



April 24, 1945. P. P. ANDERSON, JR 2,374,521

REFRIGERATION Filed April 18, 1941 BY INVENTORJfiMI 4M M A TTOENEYPatented Apr. 24, 1945 2,374,521 REFRIGERATION Philip P. Anderson, Jr.,Evansville, Ind., assignmto Serve], Inc., New York, N. Y., a corporationof Delaware Application April 18, 1941, Serial No. 389,112

Claims.

This invention relates to refrigeration, and is.

particularly concerned with withdrawal of noncondensible gases fromrefrigeration systems operating at low pressures.

During operation of refrigeration systems noncondensible gases maycollect in parts thereof to cause objectionable increase in pressure inthe system. This is particularly true in refrigeration systems of theabsorption type which operate at partial vacuum and at extremely lowpressures. The increase in pressure in the refrigeration system,resulting from the collection of non-condensible gases, is undesirablebecause the sillcincy of the system is lowered and normal operationthereof may be disturbed.

It is an object of this invention to provide an improvement for removingnon-condensible gases from refrigeration systems. This is accomplishedby employing a two-stage ejector typev of vacuum pump, the first stagebeing operated by steam and the second stage being operated by waterunder suitable pressure.

The above and other objects and advantages of the invention will bebetter understood from the following description taken in conjunctionwith the accompanying drawing forming a part of this specification, andof which the single figure more or less diagrammatically illustrates arefrigeration system embodyin the invention.

Referring to the drawing, the present invention is embodied in atwopressure absorption refrigeration system like that described inapplication Serial No. 239,762 of A. R. Thomas and P. P. Anderson, J r.,filed November 10, 1938, now Patent No. 2,282,503 granted May 12, 1942.A system of this type operates at low pressure and includes a generatoror vapor expeller III, a condenser I I, an evaporator l2, and anabsorber M which are interconnected in such a manner that the pressuredifferential in the system is maintained by liquid columns.

The disclosure in the aforementioned Thomas and Anderson application maybe considered as being incorporated in this application, and, ifdesired, reference may be had thereto for a detailed description of therefrigeration system. In Fig. 1 the generator Ill includes an outershell within which are disposed a plurality of vertical riser tubes l6having the lower ends thereof communicating with a space l1 and theupper ends thereof extending into and above the bottom of g a vessel 18.The space 19 within shell l5 forms a steam chamber about the tubes IE towhich steam is supplied through a conduit 20, as will be describedpresently. The space l9 provides for full length heating of tubes "5, avent 2| being formed at the upper end of shell IS. A conduit 22 isconnected to the lower part of shell ii for draining condensate fromspace 19.

The system operates at a partial vacuum and contains a water solution ofrefrigerant in absorbent liquid, such as, for example, a water solutionof about 40% lithium chloride by weight. With steam being suppliedthroughconduit 20 to space ill at atmospheric pressure, heat is appliedto tubes l6 whereby water vapor is expelled from solution. Theabsorption liquid is raised by gas or vapor-lift action with theexpelled water vapor forming a central core within an upwardly risingannulus of the liquid. The expelled water vapor rises more rapidly thanthe liquid with the liquid following along the inside walls of tubes 18.

The water vapor flows upwardly through the tubes or risers 16 intovessel l8 which serves as a vapor separator. Due to baiiling in vesselI8, water vapor is separated from raised absorption solution and flowsthrough conduit 23 into condenser II. II flows through a U-tube 24 intoa flash chamber 25 and from the latter through a conduit 26 intoevaporator I2.

The evaporator I2 includes a plurality of horizontal banks of tubes 21disposed one above the other and to which are secured heat transfer fins28 to provide a relatively extensive heat transfer surface. .The liquidflowing to evaporator I2 is divided in any suitable manner for flowthrough the uppermost banks of tubes 21. The dividing of liquid may beeffected by providing a liquid distributing trough 29 into which theliquid flows through the conduit 26. The water passes successivelythrough the banks of tubes which are coupled by suitable endconnections. The end connections are open to permit escape of vapor fromthe tubes, and any excess liquid is discharged from the lowermost bankof tubes 21.

- The water supplied to tubes 21 evaporates therein to produce arefrigerating or cooling effect with consequent absorption of heat fromthe surroundings, as from a stream of air flowing over the exteriorsurfaces of the tubes 21 and fins 28. The vapor formed in tubes 28passes out into end headers 38 which are connected at their lower endsto absorber I l. The flash chamber 25 is provided to take care of anyvapor flashing of liquid being fed to evaporator l2 through U-tube 24.

The flashed vapor formed in the initial cooling of the liquid flowingfrom condenser I 1 passes through a-conduit 3| into one of the headers30 and mixes with vapor formed in the evaporator l2,

The condensate formed in condenser so that disturbances in theevaporator due to vaextend lengthwise of and above the uppermosthorizontal branches of pipe banks 34. Absorption liquid is siphoned overthe walls of the liquid holders 36 to effect complete wetting of theuppermost pipe sections. Liquid drips from each horizontal pipe sectiononto the next lower pipe section, whereby all of the pipe sections arewetted with a film of liquid.

The water vapor formed in evaporator l2 passes through the headers 30into the absorber l4 where it is absorbed by the absorption liquid and,due to such absorption .of water vapor, the absorption liquid isdiluted. The diluted absorption liquid flows through a conduit 31, afirst passage in liquid heat exchanger 38, conduit 39, vessel 40 and Iconduit 4| into the lower space ll of generator i0. Water vapor isexpelled out of solution in generator ill by heating, and the solutionis raised by gas or vapor-lift action in riser tubes It, as explainedabove.

' The absorption liquid in vessel I8 is concentains the pressuredifferential between the inlet of the absorber and the upper part ofgenerator It. In operation, the liquid columns may form inconduits 31,42 and down-leg of tube 24 to the levels a, y and z, for example. Theconduits are of such size that restriction to gas flow is efl'ectedwithout appreciably restricting flow of liquid.

The liquid column formed in vessel 40 and conduit 4i provides the liquidreaction head for raising liquid infriser tubes I6 by vapor-lift action.

- The vessel 40 is ofsufllcient volume to hold the liquid differentialin the system and is of such cross-sectional area that the liquid leveltherein does not appreciably vary, so that a substantially constantreaction head is provided for lifting liquid in generator l0.

The steam chamber l9 formed by jacket l5 of generator l0 constitutes apart of a heating system which includes the conduit 20 and a boiler 41The boiler 41 is provided with a plurality of heating tubes 48 into thelower ends of which are adapted to project the flames of one or moreburners 49. The burners 49 are supplied with a suitable combustible gas,and the hot products of combustion produced by the burner flames passthrough the heating tubes 48 to heat the water in trated since watervapor has been expelled therefrom in generator in. This concentratedabsorption liquid flows through a conduit .42, a second passage inliquid heat exchanger 33, and conduit 32 into the upper part of absorberII. Thi circulation of absorption liquid results from the raising ofliquid by vapor-lift action in vertical'riser tubes l6, whereby theliquid can flow to absorber by force of gravity.

The vessel 40 is cylindrical in shape and disposed about shell lliofgenerator .lll. By arranging vessel 40 to receive heat derived from thesteam in space is, preheating of absorption liquid flowing to generatori0 is effected. The upper part of vessel '40 is connected by a conduit43 to vessel l8, so that the pressure in vessel 43 is equalized withthepressure in the upper part of generator, 10 and condenser II.

The heat liberated with absorption of water vapor in absorber i4 istransferred to a cooling medium,such as water, for example, which flowsupward through the vertically disposed pipe banks 34. The cooling mediumenters the lower ends of the pipe banks 34 through a conduit 44 andleaves the upper ends of the pipe banks 34 through a conduit 45. Theconduit 45 is connected to condenser ll whereby the same cooling mediummay be utilized to cool both condenser l l and absorber l4, and fromcondenser the cooling medium flows through a conduit 46 to waste.

The system operates at low pressures with the generator Ill andcondenser ll operating at one pressure and the evaporator l2 andabsorber l4 operating at a lower pressure, the pressure diiler- I4 andreturn from the latter to the generator I0 the boiler and produce steam.The hot gases pass from the tubes 43 to'risers or flues 50. The steamformed in boiler 41 serves as a heating medium for the refrigerationsystem and flows through the conduit 20 to the steam chamber l9, a valve5| being connected in the conduit to control, flow of steamtherethroush- During'operation of the refrigeration systemnon-condensible gases may collect therein, and in condenser ll suchgases flow toward the deadend or bottom part of the condenser. To removenon-condensible gases from condenser H to the lower pressure side ofthesystem, a liquid siphon trap 52 is provided in conduit 24, asdescribed in my application Serial No. 350,883, filed August 3,

1940. The, siphon trap 52 may be of any desired shape and is shown inthe form of a complete circular loop in the down-leg of U-tube 24.

The liquid formed in condenser flows into loop 52. When the circularloop is completely filled with liquid to the level p, the liquid issiphoned from the loop into the down-leg of U- tube 24. The gas in thedown-leg of U-tube 24,

between the loop 52 and liquid level 2, is trapped by the liquidsiphoned from the loop. Immediately after liquid has siphoned from theloop, gas passes .from the bottom part of condenser ll through the loop52 into the down-leg of U-tube 24. When liquid flowing from condenser llagain reaches the level p in-the circular loop 52, liquid is againsiphoned into the down-leg of the tube 24. In this manner gas passingfrom condenser Ii into the downsleg of tube 24, before the liquid sealis formed in loop 52, is segregated by the liquid subsequently siphonedinto the down-leg of the tube.

The gas segregated between the successive bodies of liquid siphoned fromloop 52 is compressed by the siphoned liquid and passes through theU-tube by thev gravity flow of liquid from.

ential therebetween being maintained by liquid columns. Thus, the liquidcolumn formed in tube 24 maintains the pressure difierential betweencondenser I i and evaporator i2, the liquid column in conduit3lmaintains the pressure differential between the outlet of absorber i4and generator i0, and the liquid column formed in conduit 32 andconnected parts including conduit 42 maincondenser ii to evaporator I2.In this way non- 'oondensible gases collecting in the'upper part ofgenerator l0 and'condenser ll are removed or transferred from theseparts of the system to the evaporator l2 and absorber I 4 to which thevacuum pump embodying the present invention is connected for removingnon-condensible gases from the refrigeration system.

In accordance with this invention a two-stage ejector type of vacuumpump is provided to withdraw non-condensible gases from absorber I4through a conduit 53. The conduit 53 is provided with the two-stageejector type vacuum .pump

with a valve 54 and extends into the bottom part of absorber l4. Theopen end of conduit 53 is disposed at an intermediate region of absorberl4 inasmuch as the non-condensible gases are swept by the high velocityof the water vapor to the center part of the absorber which is thefarthest point in the path of flow for the gases from the lower ends ofheaders 36.

The end of conduit-53 outside of absorber I4 is connected to the inletend of a Venturi tube 55 having a nozzle 56 and which serves as a firststage of an ejector to which steam is'delivered at substantiallyatmospheric pressure from a suitable source of supply. Since generator16 of the refrigeration system is supplied with steam at atmospheric.pressure through conduit 20 from steam boiler 41, the conduit 51 throughwhich steam is supplied to nozzle 56 of Venturi tube 55 is connected toconduit 20. The diverging side or discharge end of Venturi tube 55 isconnected to the inlet or converging side of a second Venturi tube 58having a nozzle 59 therein to which water under suitable pressure isdelivered through a conduit 60. The Venturi tube 58 serves as the secondstage of the ejector. The conduit 60 is connected to conduit 44 throughwhich water flows from a suitable source of supply to effect cooling ofabsorber l4. Suitable valves BI and 62 are connected in conduits 51 and60, respectively, to control flow of steam and water to the two stagesof the ejector,

When it is desired to remove non-condensible gases from therefrigeration system during operation of the latter, the steam and watersupply valves 6| and 62 are opened to start operation of the two-stageejector. After the pressure in conduit 53 is lowered sufficiently at theregion between the throat of Venturi tube 55 and valve 54 by ejectoraction, the valve 54 is opened to permit withdrawal of gases from thebottom part of absorber H. The withdrawn gases pass through conduit 53and mix with steam discharged from the nozzle 56 in Venturi tube 55. Thesteam discharged from nozzle 56 acquires a high velocity to produce asuction effect for withdrawing gases from absorber '4. In the secondstage the water passing through the nozzle 59 in Venturi tube 58acquires a high velocity whereby a suction effect is produced to effectwithdrawal of the steam and gas mixture from the Venturi tube 55 of thefirst stage. Condensation of steam occurs in Venturi tube 58 and thewater, together with the condensate and noncondensible gases, aredischarged throughconduit 63 to atmosphere.

After substantially all of the noncondensible gases are removed from therefrigeration system, as may be determined by a suitable pressureindicating device, for example, the valve 54 is first closed to shut offthe system from the atmosphere, and thereafter the steam and watersupply valves BI and 62 are closed.

A two-stage ejector of the character just described is particularlyadvantageous in that it is relatively inexpensive, and at the same timeextremely low pressures can be produced by such a vacuum pump. In thekind of refrigeration system illustrated and described and in which theinvention is embodied, the normal operating pressure in the absorber l4may be as low as 5 to 6 mm. mercury. A partial vacuum of the lowillustrated an described. This is not true of an ordinary water ejectoror aspirator because the pressure usually maintained in the absorber islower than the vapor pressure of the water used in the ejector. In thetwo-stage ejector described above, the water may be supplied to thesecond stage from the usual source of city supply which may be at apressure of about 30 pounds per square inch or higher.

While a single embodiment of the invention has been shown and described,it will be apparent to those skilled in the art that variousmodifications and changes may be made without departing from the spiritand scope of the invention, as pointed out in the following claims.

What is claimed is:

1. In an absorption type refrigeration system having a plurality ofinterconnected parts including an evaporator in which evaporation ofliquid refrigerant takes place, an absorber comprising an elongatedvessel having openings at opposite ends through which refrigerant vaporis introduced from said evaporator, and a heat receiving part, means toheat said heat receiving part by steam delivered from a source ofsupply, means to effect cooling of said absorber by cooling waterdelivered from a source of supply, a vacuum pump, and a conduitconnectin said pump and an intermediate region of said vesselconstituting the farthest point in the path of flow of noncondensiblegases swept into such region by the refrigerant vapor, said vacuum pumpcomprising a two-stage ejector, the first stage of said ejector beingoperable'by steam from said source of supply and the second stage ofsaid ejector being connected to said first stage and operable by watersupplied thereto under pressure from its source of supply.

In an absorption type refrigeration system having a plurality ofinterconnected vessels normally maintained at a partial vacuum andincluding a vessel into the upper part of which is introducedrefrigerant vapor, a vacuum pump,

value just mentioned can readily be obtained and a conduit connectingsaid pump and a region at or adjacent to the bottom part of said vesseland to which region non-condensible gases are swept and tend to collectby the sweeping effect of the refrigerant vapor introduced into saidvessel, such region in the bottom part of said vessel connected to saidpump by said conduit normally being a part of the vapor space in saidvessel, said vacuum pump comprising an ejector operable by steam toeliect removal of non-condensible gases through said conduit from saidregion.

3. In an absorption type refrigeration system having a plurality ofinterconnected parts normally maintained at a partial vacuum andincluding a vessel into which is introduced refrigerant vapor, a vacuumpump, and a conduit connecting said pump and said vessel, said vacuumpump comprising a two-stage ejector operable to effect removal ofnon-condensible gases through said conduit from said vessel, the firststage of said ejector being operable by vapor and the second stage ofsaid ejector being connected to said first stage and operable by liquidsupplied thereto under pressure.

4. In a refrigeration system of the absorption type having a pluralityof interconnected parts includin an evaporator in which evaporation ofliquid refrigerant takes places, an absorber in open communication withsaid evaporator and into which absorption solution is conducted, and aheat receiving part, means to heat said heat receiving part by a heatingmedium delivered from a source of supply, a vacuum pump, a conduitconnecting said pump and a region of said absorber constituting thefarthest point in the path of flow of non-condensible gases swept into,such region by the refrigerant vapor formed -:ir i'* said evaporator,means for delivering heating medium from said source of supply tosaid'pump,

said vacuum pump utilizing the heating medium to effect removal ofnon-condensible gases through said conduit from saidregion, a control insaid conduit for controlling the removal of non-condensible gases fromthe system by said pump. a conduit connecting said pump and a region ofsaid vessel constituting the farthest point in the path of flow ofnon-condensible gases sweptinto such region by the refrigerant vaporintroduced into said vessel, and means for delivering-heating mediumfrom said source of supply to said pump, said vacuum pump utilizing themedium to effect removal of non-condensible gases through said conduit,a control in said conduit for controlling removal of non-condensiblegases from the system by said pump, and another control for controllingthe delivery of heating medium to said pump.

6. In an absorption type refrigeration system having a plurality ofinterconnected parts in cluding a heat rejecting part into whichrefrigerant vapor is introduced and a heat receiving.

part, means to heat said heat receiving part by a heating mediumdelivered from a source of supply, means to efiect cooling of said heatrejecting part by cooling water delivered from a source of supp y avacuum pump, a conduit connecting said pump and said heat rejectingpart, means for delivering heating medium from said source of supply tosaid pump, and means for delivering cooling water from said source ofsupply to said pump, said pump utilizing the heating medium and water toeffect removal of noncondensible gases from the refrigeration systemthrough the conduit.

7. In an absorption type refrigeration system having a plurality ofinterconnected parts including a heat rejecting part into whichrefrigerant vapor is introduced and a heat receiving part, means to heatsaid heat receiving part by a heating medium delivered from a source ofsupply, a vacuum pump, a conduit connecting said vacuum pump and saidheat rejecting part and through which non-condensible gases are removedfrom the system by said pump, said vacuum pump comprising a two-stageejector, means for delivering heating medium from said source of supplyto the first stage of said ejector, and means for delivering water tosaid second stage of said ejector, said ejector utilizing" the heatingmedium and water to effect removal of non-condensible gases from therefrigeration system through said conduit.

8. In an absorption type refrigeration system having a plurality ofparts interconnected for flow of fluids therein and including a heatrejecting part and a heat receiving part, a steam boiler connected todeliver steam to heat said heat receiving part, means to effect coolingof said heat i rejecting part by cooling water delivered from a sourceof supply, a vacuum pump, a conduit connecting said vacuum pump and aregion of said system into which non-condensible gases are swept byfluid flowing in the system, said vacuum cluding a heat receiving part,an evaporator in which evaporation of liquid refrigerant takes place ina partial vacuum, an absorber always in open communication with saidevaporator and comprising an elongated vessel having openings atopposite ends through which refrigerant vapor is introduced at highvelocity from said evaporator, means to introduce absorption liquid intosaid vessel, means to heat said heat receiving part by a vaporous heatinmedium delivered from a source of supply, a vacuum pump, a con-.

duit connecting said pump and an intermediate region of said vesselconstituting the farthest point in the path of flow of non-condensible'gases swept into such region by the refrigerant vapor, and means fordelivering the vaporous heating medium from said source of supply tosaid vacuum pump, said vacuum pump utilizing the vaporous heating mediumto effect removal of non-condensible gases from said refrigerationsystem through said conduit. v

10. In an absorption type refrigeration system having a plurality ofinterconnected vessels normally maintained at a partial vacuum andincluding a first vessel, into the upper part of which is introducedrefrigerant vapor, and a heat receiving vessel, means to heat said heatreceiving vessel by a heating medium delivered from a source of supply,a vacuum pump,a conduit connecting said pump and a region at or adjacentto the bottom part of said first vessel and to which regionnon-condensible gases are swept and tend to collect by the sweepingeffect of the refrigerant vapor introduced into said first vessel, suchre, gion in the 'bottom part of said first vessel connected to said pumpby said conduit normally being a part of the vapor space in said firstvessel, and means for delivering heating medium from said source ofsupply to saidvacuum pump, said vacuum pump utilizing the heating mediumto effect removal ofnon-condensible gases from the refrigeration systemthrough said conduit.

PHILIP P. ANDERSON, JR.

